[Solved] New TreeView does not connect to C++ model.

Hello guys, I was waiting long time before Qt 5.5 has been released because of new TreeView component.
I am trying in agony to make it work with my model in C++ for a week.
So, I am completely stuck in understanding how all this "kitchen" works.

@Kofr@p3c0
I need some help regarding re-ordering of the item of the QAbstractItemModel. I have put a MouseArea in the itemDelegate which allows me to drag an item. I need some help to call C++ function of the QAbstractItemModel to move items to support the dynamic re-ordering. Kindly advice